Reviewed-by: Steve Wahl <[email protected]> On Sun, Jan 23, 2022 at 10:38:46AM -0800, Yury Norov wrote: > In some cases, arch/x86 code calls cpumask_weight() to check if any bit of > a given cpumask is set. We can do it more efficiently with cpumask_empty() > because cpumask_empty() stops traversing the cpumask as soon as it finds > first set bit, while cpumask_weight() counts all bits unconditionally. > > Signed-off-by: Yury Norov <[email protected]> > --- > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 14 +++++++------- > arch/x86/mm/mmio-mod.c | 2 +- > arch/x86/platform/uv/uv_nmi.c | 2 +- > 3 files changed, 9 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c > b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > index b57b3db9a6a7..e23ff03290b8 100644 > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > @@ -341,14 +341,14 @@ static int cpus_mon_write(struct rdtgroup *rdtgrp, > cpumask_var_t newmask, > > /* Check whether cpus belong to parent ctrl group */ > cpumask_andnot(tmpmask, newmask, &prgrp->cpu_mask); > - if (cpumask_weight(tmpmask)) { > + if (!cpumask_empty(tmpmask)) { > rdt_last_cmd_puts("Can only add CPUs to mongroup that belong to > parent\n"); > return -EINVAL; > } > > /* Check whether cpus are dropped from this group */ > cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask); > - if (cpumask_weight(tmpmask)) { > + if (!cpumask_empty(tmpmask)) { > /* Give any dropped cpus to parent rdtgroup */ > cpumask_or(&prgrp->cpu_mask, &prgrp->cpu_mask, tmpmask); > update_closid_rmid(tmpmask, prgrp); > @@ -359,7 +359,7 @@ static int cpus_mon_write(struct rdtgroup *rdtgrp, > cpumask_var_t newmask, > * and update per-cpu rmid > */ > cpumask_andnot(tmpmask, newmask, &rdtgrp->cpu_mask); > - if (cpumask_weight(tmpmask)) { > + if (!cpumask_empty(tmpmask)) { > head = &prgrp->mon.crdtgrp_list; > list_for_each_entry(crgrp, head, mon.crdtgrp_list) { > if (crgrp == rdtgrp) > @@ -394,7 +394,7 @@ static int cpus_ctrl_write(struct rdtgroup *rdtgrp, > cpumask_var_t newmask, > > /* Check whether cpus are dropped from this group */ > cpumask_andnot(tmpmask, &rdtgrp->cpu_mask, newmask); > - if (cpumask_weight(tmpmask)) { > + if (!cpumask_empty(tmpmask)) { > /* Can't drop from default group */ > if (rdtgrp == &rdtgroup_default) { > rdt_last_cmd_puts("Can't drop CPUs from default > group\n"); > @@ -413,12 +413,12 @@ static int cpus_ctrl_write(struct rdtgroup *rdtgrp, > cpumask_var_t newmask, > * and update per-cpu closid/rmid. > */ > cpumask_andnot(tmpmask, newmask, &rdtgrp->cpu_mask); > - if (cpumask_weight(tmpmask)) { > + if (!cpumask_empty(tmpmask)) { > list_for_each_entry(r, &rdt_all_groups, rdtgroup_list) { > if (r == rdtgrp) > continue; > cpumask_and(tmpmask1, &r->cpu_mask, tmpmask); > - if (cpumask_weight(tmpmask1)) > + if (!cpumask_empty(tmpmask1)) > cpumask_rdtgrp_clear(r, tmpmask1); > } > update_closid_rmid(tmpmask, rdtgrp); > @@ -488,7 +488,7 @@ static ssize_t rdtgroup_cpus_write(struct > kernfs_open_file *of, > > /* check that user didn't specify any offline cpus */ > cpumask_andnot(tmpmask, newmask, cpu_online_mask); > - if (cpumask_weight(tmpmask)) { > + if (!cpumask_empty(tmpmask)) { > ret = -EINVAL; > rdt_last_cmd_puts("Can only assign online CPUs\n"); > goto unlock; > diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c > index 933a2ebad471..c3317f0650d8 100644 > --- a/arch/x86/mm/mmio-mod.c > +++ b/arch/x86/mm/mmio-mod.c > @@ -400,7 +400,7 @@ static void leave_uniprocessor(void) > int cpu; > int err; > > - if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0) > + if (!cpumask_available(downed_cpus) || cpumask_empty(downed_cpus)) > return; > pr_notice("Re-enabling CPUs...\n"); > for_each_cpu(cpu, downed_cpus) { > diff --git a/arch/x86/platform/uv/uv_nmi.c b/arch/x86/platform/uv/uv_nmi.c > index 1e9ff28bc2e0..ea277fc08357 100644 > --- a/arch/x86/platform/uv/uv_nmi.c > +++ b/arch/x86/platform/uv/uv_nmi.c > @@ -985,7 +985,7 @@ static int uv_handle_nmi(unsigned int reason, struct > pt_regs *regs) > > /* Clear global flags */ > if (master) { > - if (cpumask_weight(uv_nmi_cpu_mask)) > + if (!cpumask_empty(uv_nmi_cpu_mask)) > uv_nmi_cleanup_mask(); > atomic_set(&uv_nmi_cpus_in_nmi, -1); > atomic_set(&uv_nmi_cpu, -1); > -- > 2.30.2 >
-- Steve Wahl, Hewlett Packard Enterprise
